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The Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring. [1] Friedel–Crafts reactions are of two main types: alkylation reactions and acylation reactions.
For example, Friedel–Crafts acylation uses acetyl chloride (CH 3 COCl) as the agent and aluminum chloride (AlCl 3) as a catalyst to add an acetyl group to benzene: [2] Friedel-Crafts acylation of benzene by ethanoyl chloride. This reaction is an example of electrophilic aromatic substitution.
Acetylferrocene is prepared by Friedel-Crafts acylation of ferrocene, usually with acetic anhydride (Ac 2 O): . Fe(C 5 H 5) 2 + Ac 2 O → (C 5 H 5)Fe(C 5 H 4 Ac) + HOAc. The experiment is often conducted in the instructional laboratory to illustrate acylation as well as chromatographic separations.
Oxalyl chloride reacts with aromatic compounds in the presence of aluminium chloride to give the corresponding acyl chloride in a process known as a Friedel-Crafts acylation. [15] [16] The resulting acyl chloride can be hydrolysed to form the corresponding carboxylic acid.
Freund reaction; Friedel–Crafts acylation; Friedel–Crafts alkylation; Friedländer synthesis; ... Gewald reaction; Gibbs phthalic anhydride process; Gilman reagent;
While nucleophilic acyl substitution reactions can be base-catalyzed, the reaction will not occur if the leaving group is a stronger base than the nucleophile (i.e. the leaving group must have a higher pK a than the nucleophile). Unlike acid-catalyzed processes, both the nucleophile and the leaving group exist as anions under basic conditions.
2-Acetylfuran was prepared by Ashina in 1914 via the reaction of the methyl Grignard reagent on 2-furonitrile. [3] Modern industrial synthesis generally involves the Friedel–Crafts acylation of furan with acetic anhydride.
Similarly, in Friedel-Crafts acylation, a Lewis acid assists in the generation of an acylium ion from an acid chloride (or occasionally acid anhydride). Although the acylium ion is often assumed to be the active intermediate, [ 37 ] there is evidence that the protonated acylium dication is the active electrophile that undergoes subsequent ...